Try not to make it broken though or you could choose one that already exists. I'll start: Extremespeed on Snorlax it would be really good with Belly Drum but not broken because of faster Ghost, Rock, Steel types. It would also be pretty hard to set up while taking a hit at the same time.
This gives him a way to patch up his awful defense while gaining speed and even more power. Still wouldn't be broken because he can only recover with rest and it's really hard to find time to switch him in.
My Sacred Gold Team http://i.imgur.com/BRUVZBM.png